The generator start-up sequence is critical to power system restoration after black-out.To avoid the inconformity of optimization goals and the repeat call of Dijkstra method，a new algorithm of optimizing the start-up sequence of generator based on Dijkstra method is proposed.The modification for the weight of the branches and generators are proposed.Based on the modified weights，a priority index considering the branch weight，generator start-up requirement and ramping rate is proposed to optimize the generator start-up sequence.Furthermore，a method of bypassing the backtracking is proposed and the logic to call Dijkstra is improved to prevent the repetition of Dijkstra and reduce the computation cost.The IEEE 39-bus system is used for validation of the optimization algorithm.